Exhibit 1.1

Execution Version

Alliant Energy Corporation

5.750% Fixed-to-Fixed Reset Rate Junior Subordinated Notes Due 2056

Underwriting Agreement

September 23, 2025

BofA Securities, Inc.

One Bryant Park

New York, New York 10036

MUFG Securities Americas Inc.

1221 Avenue of the Americas, 6th Floor

New York, New York 10020

Barclays Capital Inc.

745 Seventh Avenue

New York, New York 10019

Goldman Sachs & Co. LLC

200 West Street

New York, New York 10282

J.P. Morgan Securities LLC

383 Madison Avenue

New York, New York 10179

As Representatives (as defined below) of the several Underwriters (as defined below)

Ladies and Gentlemen:

Alliant Energy Corporation, a Wisconsin corporation (the “Company”), confirms its agreement with BofA Securities, Inc., MUFG Securities Americas Inc., Barclays Capital Inc., Goldman Sachs & Co. LLC, and J.P. Morgan Securities LLC, and each of the other underwriters named in Schedule A hereto (collectively, the “Underwriters,” which term shall also include any underwriter substituted as hereinafter provided in Section 10 hereof), for whom BofA Securities, Inc., MUFG Securities Americas Inc., Barclays Capital Inc., Goldman Sachs & Co. LLC, and J.P. Morgan Securities LLC are acting as representatives (in such capacity, the “Representatives”), with respect to the issue and sale by the Company and the purchase by the Underwriters, acting severally and not jointly, of the respective principal amounts set forth on Schedule A hereto of $725,000,000 principal amount of the Company’s 5.750% Fixed-to-Fixed Reset Rate Junior Subordinated Notes due 2056 (the “Securities”). The Securities will be issued pursuant to an indenture to be dated as of September 26, 2025 (the “Base Indenture”) between the Company and The Bank of New York Mellon Trust Company, N.A., as trustee (the “Trustee”). The term “Indenture,” as used herein, includes the Base Indenture, as supplemented by a supplemental indenture to be executed in

connection with the offering of the Securities, establishing the form and terms of the Securities pursuant to Section 301 of the Base Indenture (the “Supplemental Indenture”). The Securities are to be issued in book-entry form and will be registered in the name of Cede & Co. as nominee of The Depository Trust Company (“DTC”) pursuant to the blanket letter agreement (the “DTC Agreement”), between the Company and DTC.

The Company understands that the Underwriters propose to make a public offering of the Securities as soon as the Representatives deem advisable after this underwriting agreement (this “Agreement”) has been executed and delivered. This Agreement, the DTC Agreement, the Securities and the Indenture are referred to herein as the “Transaction Documents.”

The Company has filed with the Securities and Exchange Commission (the “Commission”) an automatic shelf registration statement on Form S-3 (No. 333-276062), as amended, including a base prospectus (the “Base Prospectus”), for the registration of certain securities, including the Securities, under the Securities Act of 1933, as amended (the “1933 Act”), and the offering thereof from time to time in accordance with Rule 415 of the rules and regulations of the Commission under the 1933 Act (the “1933 Act Regulations”), which automatic shelf registration statement and amendment each became effective under the 1933 Act upon filing with the Commission. Promptly after execution and delivery of this Agreement, the Company will prepare and file a prospectus supplement relating to the Securities in accordance with the provisions of Rule 430B (“Rule 430B”) of the 1933 Act Regulations and paragraph (b) of Rule 424 (“Rule 424(b)”) of the 1933 Act Regulations. Any information included in such prospectus supplement that was omitted from the Registration Statement at the time it first became effective but that is deemed to be a part of and included in such registration statement pursuant to Rule 430B is referred to as “Rule 430B Information.” Such registration statement, at any given time, including the amendments thereto to such time, the exhibits and schedules thereto, at such time, and the Rule 430B Information, is referred to herein as the “Registration Statement.” The final prospectus supplement, together with the Base Prospectus, in the form first furnished to the Representatives by the Company for use in connection with the offering of the Securities, is referred to herein as the “Prospectus.” A “preliminary prospectus” shall be deemed to refer to any preliminary prospectus supplement, together with the Base Prospectus, used in connection with the offering of the Securities that omitted the Rule 430B Information. For the purposes of this Agreement, all references to the “Registration Statement,” the “Prospectus” or any preliminary prospectus shall also be deemed to include all documents incorporated therein by reference pursuant to Item 12 of Form S-3 under the 1933 Act at such time and the documents otherwise deemed to be a part thereof or included therein by the 1933 Act Regulations. For purposes of this Agreement, all references to the Registration Statement, Prospectus or preliminary prospectus or to any amendment or supplement to any of the foregoing shall be deemed to include any copy filed with the Commission pursuant to its Electronic Data Gathering, Analysis and Retrieval system (“EDGAR”).

All references in this Agreement to financial statements and schedules and other information which are “contained,” “included” or “stated” (or other references of like import) in the Registration Statement, Prospectus or preliminary prospectus shall be deemed to mean and include all such financial statements and schedules and other information which are incorporated by reference in or

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otherwise deemed by 1933 Act Regulations to be a part of or included in, as of such applicable date, the Registration Statement, Prospectus or preliminary prospectus, as the case may be.

SECTION 1.Representations and Warranties. The Company represents and warrants to each Underwriter as of the date hereof, as of the Applicable Time referred to in Section 1(a) hereof and as of the Closing Time referred to in Section 2(b) hereof, and agrees with each Underwriter, as follows:

(a)Registration Statement, Prospectus and Disclosure at Time of Sale. The Company meets the requirements for use of Form S-3 under the 1933 Act. The Registration Statement is an “automatic shelf registration statement,” as defined in Rule 405 (“Rule 405”) of the 1933 Act Regulations, that automatically became effective not more than three years prior to the date hereof and no stop order suspending the effectiveness of the Registration Statement has been issued under the 1933 Act and no proceedings for that purpose have been instituted or are pending or, to the knowledge of the Company, are contemplated by the Commission, and any request on the part of the Commission for additional information has been complied with. The Company has not received from the Commission any notice pursuant to Rule 401(g)(2) (“Rule 401(g)(2)”) of the 1933 Act Regulations objecting to use of the automatic shelf registration statement form and the Company has not otherwise ceased to be eligible to use the automatic shelf registration form.

At the time the Registration Statement became effective (including without limitation any effective dates of any amendments thereto and each deemed effective date with respect to the Underwriters pursuant to Rule 430B(f)(2) of the 1933 Act Regulations) and at the Closing Time, the Registration Statement and any amendments and supplements thereto complied or will comply, as the case may be, in all material respects with the requirements of the 1933 Act and the 1933 Act Regulations and the Trust Indenture Act of 1939, as amended (the “1939 Act”), and the rules and regulations of the Commission under the 1939 Act (the “1939 Act Regulations”), and did not or will not, as the case may be, contain an untrue statement of a material fact or omit to state a material fact required to be stated therein or necessary to make the statements therein not misleading and the Indenture complied and will comply in all material respects with the requirements of the 1939 Act. Neither the Prospectus nor any amendments or supplements thereto, at the time the Prospectus or any such amendment or supplement was issued and at the Closing Time, included or will include an untrue statement of a material fact or omitted or will omit to state a material fact necessary in order to make the statements therein, in the light of the circumstances under which they were made, not misleading. The representations and warranties in this subsection shall not apply to statements in or omissions from the Registration Statement or Prospectus made in reliance upon and in conformity with information furnished to the Company in writing by any Underwriter through the Representatives expressly for use in the Registration Statement (or any amendment thereto) or Prospectus (or any amendment thereto), it being understood and agreed that the only such information consists of the information contained in Schedule D hereto.

Each preliminary prospectus and the prospectus filed as part of the Registration Statement as originally filed or as part of any amendment thereto, or filed pursuant to Rule 424 under the 1933 Act, complied when so filed in all material respects with the 1933 Act Regulations and each preliminary prospectus and the Prospectus delivered or to be delivered to the Underwriters for use in

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connection with this offering was or will be identical to the electronically transmitted copies thereof filed with the Commission pursuant to EDGAR, except to the extent permitted by Regulation S-T.

As of the Applicable Time (as defined below), neither (x) the Issuer Free Writing Prospectus(es) (as defined below) listed on Schedule B hereto and the Statutory Prospectus (as defined below), all considered together (collectively, the “General Disclosure Package”), nor (y) any individual Issuer Free Writing Prospectus, when considered together with the General Disclosure Package, will include any untrue statement of a material fact or omit to state any material fact necessary in order to make the statements therein, in the light of the circumstances under which they were made, not misleading.

At the time of filing the Registration Statement, at the earliest time thereafter that the Company or another offering participant made a bona fide offer (within the meaning of Rule 164(h)(2) of the 1933 Act Regulations) of the Securities and at the date hereof, the Company was not and is not an “ineligible issuer,” as defined in Rule 405.

As used in this subsection and elsewhere in this Agreement:

“Applicable Time” means 3:30 p.m., New York City time, on the date of this Agreement.

“Statutory Prospectus” as of any time means the prospectus relating to the Securities that is included in the Registration Statement immediately prior to that time, including any document incorporated by reference therein and any preliminary or other prospectus supplement deemed to be a part thereof.

“Issuer Free Writing Prospectus” means any “issuer free writing prospectus,” as defined in Rule 433 (“Rule 433”) of the 1933 Act Regulations, relating to the Securities that (i) is required to be filed with the Commission by the Company, or (ii) is exempt from filing pursuant to Rule 433(d)(5)(i) because it contains a description of the Securities or of the offering that does not reflect the final terms, in each case in the form filed or required to be filed with the Commission or, if not required to be filed, in the form retained in the Company’s records pursuant to Rule 433(g) or is exempt from filing pursuant to Rule 433(d)(8)(i) relating to road shows.

Each Issuer Free Writing Prospectus, as of its issue date and at all subsequent times through the completion of the public offer and sale of the Securities or until any earlier date that the issuer notified or notifies the Representatives as described in the next sentence, did not, does not and will not include any information that conflicted, conflicts or will conflict with the information contained in the Registration Statement or the Prospectus, including any document incorporated by reference therein and any preliminary or other prospectus deemed to be a part thereof that has not been superseded or modified. If at any time following issuance of an Issuer Free Writing Prospectus there occurred or occurs an event or development as a result of which such Issuer Free Writing Prospectus included or would include an untrue statement of a material fact or omitted or would omit to state a material fact necessary in order to make the statements therein, in the light of the circumstances, not misleading, the Company has notified or will notify promptly the Representatives so that any use of such Issuer Free Writing Prospectus may cease until it is amended or supplemented. The foregoing two sentences do not apply to statements in or omissions from any Issuer Free Writing Prospectus

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based upon and in conformity with written information furnished to the Company by any Underwriter through the Representatives expressly for use therein, it being understood and agreed that the only such information consists of the information contained in Schedule D hereto.

(b)Company is a Well-Known Seasoned Issuer. (i) At the time of filing the Registration Statement, (ii) at the time of the most recent amendment thereto for the purposes of complying with Section 10(a)(3) of the 1933 Act (whether such amendment was by post-effective amendment, by incorporated report filed pursuant to Section 13 or Section 15(d) of the Securities Exchange Act of 1934, as amended (the “1934 Act”), or by form of prospectus), and (iii) as of the date hereof, the Company was and is a “well-known seasoned issuer” as defined in Rule 405.

(c)Incorporated Documents. The documents incorporated by reference or deemed to be incorporated by reference in the Registration Statement, the Statutory Prospectus and the Prospectus, at the time they were or hereafter are filed with the Commission, complied or will comply, as the case may be, in all material respects with the requirements of the 1934 Act and the rules and regulations of the Commission thereunder (the “1934 Act Regulations”), as applicable, and, when read together with the other information in the Registration Statement, the Statutory Prospectus and the Prospectus, did not or will not, as the case may be, contain an untrue statement of a material fact or omit to state a material fact required to be stated therein or necessary to make the statements therein not misleading. The description of regulatory matters to which the Company is subject, as disclosed in the Company’s filings with the Commission under the 1934 Act and the 1934 Act Regulations and as incorporated by reference into the Registration Statement, is true and correct in all material respects, except to the extent such description in any specific filing has been superseded, updated or supplemented by such description in a subsequent filing under the 1934 Act or the 1934 Act Regulations made prior to the date hereof or by such description in the Statutory Prospectus and the Prospectus.

(d)Independent Registered Public Accounting Firm. Deloitte & Touche LLP, which has audited certain financial statements of the Company and its consolidated subsidiaries and delivered its report with respect to the audited financial statements of the Company and its consolidated subsidiaries and the related notes and schedules included or incorporated by reference in the Registration Statement, the Statutory Prospectus and the Prospectus, is an independent registered public accounting firm with respect to the Company and its consolidated subsidiaries as required by the 1933 Act and the rules of the Public Company Accounting Oversight Board.

(e)Financial Statements. The financial statements of the Company and its consolidated subsidiaries, together with the related notes and schedules, included or incorporated by reference in the Registration Statement, the Statutory Prospectus and the Prospectus present fairly in all material respects the financial position of the Company and its consolidated subsidiaries as of and at the dates indicated and the statements of income, changes in common equity and cash flows of the Company and its consolidated subsidiaries for the periods specified; said financial statements have been prepared in conformity with generally accepted accounting principles (“GAAP”) applied on a consistent basis throughout the periods involved. The supporting schedules included in the Registration Statement, if any, present fairly in all material respects in accordance with GAAP the information required to be stated therein. The selected financial data and the summary financial

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information included in the Statutory Prospectus and the Prospectus present fairly in all material respects the information shown therein and have been compiled on a basis consistent with that of the audited financial statements included or incorporated by reference in the Registration Statement. The interactive data in eXtensible Business Reporting Language (“XBRL”) incorporated by reference into the Registration Statement, the Statutory Prospectus and the Prospectus present fairly in all material respects the information called for and was prepared in accordance with the Commission’s rules and guidelines applicable thereto.

(f)No Material Adverse Change in Business. Since the respective dates as of which information is given in the Registration Statement, the General Disclosure Package and the Prospectus, except as otherwise stated therein: (i) neither the Company nor any of its subsidiaries has sustained any material loss or interference with its business from fire, explosion, flood or other calamity, whether or not covered by insurance, or from any labor dispute or court or governmental action, order or decree; (ii) there has been no material adverse change in the condition, financial or otherwise, earnings or business affairs of the Company and its consolidated subsidiaries considered as one enterprise or on the performance by the Company of its obligations under, and consummate the transactions contemplated by, the Transaction Documents, whether or not arising in the ordinary course of business, nor have there been any developments involving a prospective material adverse change of the Company and its consolidated subsidiaries considered as one enterprise, whether or not arising in the ordinary course of business (any such change or effect, a “Material Adverse Effect”); (iii) there have been no transactions entered into by the Company or any of its consolidated subsidiaries, other than those in the ordinary course of business, which are material with respect to the Company and its consolidated subsidiaries considered as one enterprise; and (iv) except for regular dividends on the common stock, par value $0.01 per share, of the Company (the “Common Stock”), there has been no dividend or distribution of any kind declared, paid or made by the Company on any class of its capital stock.

(g)Good Standing of the Company. The Company has been duly organized and is validly existing as a corporation under the laws of the State of Wisconsin and has corporate power and authority to own, lease and operate its properties and to conduct its business as described in the General Disclosure Package and the Prospectus and to enter into and perform its obligations under the Transaction Documents; and the Company is duly qualified as a foreign corporation to transact business and is in good standing in each other jurisdiction in which such qualification is required, whether by reason of the ownership or leasing of property or the conduct of business, except where the failure so to qualify or to be in good standing would not result in a Material Adverse Effect;

(h)Significant Subsidiaries. Each “significant subsidiary” of the Company (as such term is defined in Rule 1-02(w) of Regulation S-X) (each, a “Significant Subsidiary” and, collectively, the “Significant Subsidiaries”) has been duly organized and is validly existing as a corporation or a limited liability company under the laws of the jurisdiction of its formation, has corporate or other power and authority to own, lease and operate its properties and to conduct its business as described in the General Disclosure Package and the Prospectus and is duly qualified to transact business and is in good standing in each foreign jurisdiction in which such qualification is required, whether by reason of the ownership or leasing of property or the conduct of business, except where the failure so to qualify or to be in good standing would not result in a Material Adverse Effect; except as

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otherwise disclosed in the Registration Statement, the General Disclosure Package and the Prospectus, all of the outstanding equity interests of each such Significant Subsidiary have been duly authorized and validly issued and all of the issued and outstanding shares of the capital stock of each such Significant Subsidiary are owned by the Company, free and clear of any security interest, mortgage, pledge or lien that reasonably would be expected to result in a Material Adverse Effect. None of the outstanding equity interests of any Significant Subsidiary was issued in violation of the preemptive or similar rights of any other holder of equity interests of such Significant Subsidiary that reasonably would be expected to result in a Material Adverse Effect. The only subsidiaries of the Company are (i) the Significant Subsidiaries and (ii) certain other subsidiaries which do not constitute a “significant subsidiary” of the Company as defined in Rule 1-02(w) of Regulation S-X;

(i)Capitalization. The authorized, issued and outstanding capital stock of the Company as of September 17, 2025 was 257,053,590 shares of Common Stock outstanding (except for subsequent issuances, if any, pursuant to (i) this Agreement, (ii) existing reservations, agreements or employee benefit plans, (iii) the exercise of convertible securities or options outstanding on such date, (iv) any dividend reinvestment plan, or (v) sales of Common Stock made pursuant to that certain Distribution Agreement, dated May 9, 2025, by and among the Company, the Agents named therein and the Forward Purchasers named therein, including pursuant to forward confirmations entered into pursuant to such agreement). All of the issued and outstanding shares of capital stock of the Company have been duly and validly authorized and issued and are fully paid and non-assessable and none of the outstanding shares of capital stock of the Company was issued in violation of any preemptive or other similar rights of any securityholder of the Company. The Company is a “holding company” as defined under the Public Utility Holding Company Act of 2005 (the “2005 Act”). Except as described in or expressly contemplated by the Registration Statement, General Disclosure Package and the Prospectus, there are no outstanding rights (including, without limitation, preemptive or similar rights), warrants or options to acquire, or instruments convertible into or exchangeable for, any shares of capital stock or other equity interest of the Company or any of its consolidated subsidiaries, nor any contracts, commitments, agreements, understandings or arrangements of any kind relating to the issuance of any capital stock or other equity interest of the Company or any such subsidiary, any such convertible or exchangeable securities or any such rights, warrants or options; and the capital stock of the Company and the Company’s charter and bylaws conform in all material respects to the descriptions thereof contained in the Registration Statement, General Disclosure Package and the Prospectus; and all the outstanding shares of capital stock or other equity interests of each subsidiary owned, directly or indirectly, by the Company have been duly and validly authorized and issued, are fully paid and non-assessable and are owned directly or indirectly by the Company, free and clear of any lien, charge, encumbrance, security interest, restriction on voting or transfer or any other claim of any third party.

(j)Authorization of Agreement. The Company has all requisite corporate power and authority to execute and deliver this Agreement and to perform its obligations hereunder; and all action required to be taken for the due and proper authorization, execution and delivery by the Company of this Agreement and the consummation by it of the transactions contemplated hereby and thereby has been duly and validly taken. This Agreement has been duly authorized, executed and delivered by the Company.

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(k)Authorization of the Base Indenture. The Base Indenture has been duly authorized, executed and delivered by the Company and duly qualified under the 1939 Act and constitutes a valid and binding agreement of the Company enforceable against the Company in accordance with its terms, except as enforcement thereof may be limited by bankruptcy, insolvency (including, without limitation, all laws relating to fraudulent transfers), reorganization, moratorium or similar laws affecting the enforcement of creditors’ rights generally, and as enforcement thereof is subject to general principles of equity (regardless of whether enforcement is considered in a proceeding in equity or at law).

(l)Authorization of the Securities. The Securities have been duly authorized and, at the Closing Time, will have been duly executed by the Company and, when authenticated, issued and delivered in the manner provided for in the Indenture and delivered against payment of the purchase price therefor as provided for in this Agreement, will constitute valid and binding obligations of the Company, enforceable against the Company in accordance with their terms, except as the enforcement thereof may be limited by bankruptcy, insolvency (including, without limitation, all laws relating to fraudulent transfers), reorganization, moratorium or similar laws affecting enforcement of creditors’ rights generally and except as enforcement thereof is subject to general principles of equity (regardless of whether enforcement is considered in a proceeding in equity or at law) and will be in the form contemplated by, and entitled to the benefits of, the Indenture.

(m)Description of the Securities and the Indenture. The statements relating to the Securities and the Indenture contained in the Prospectus and the General Disclosure Package conform in all material respects to the terms of the Securities and the Indenture.

(n)Accuracy of Statements. The statements in each of the General Disclosure Package and Prospectus under the captions “Description of the Notes,” “Description of Debt Securities” and “Material U.S. Federal Income Tax Considerations,” insofar as such statements constitute a summary of the legal matters, documents or proceedings referred to therein, fairly present and summarize, in all material respects, the matters referred to therein.

(o)Absence of Defaults and Conflicts. Neither the Company nor any of its consolidated subsidiaries is (i) in violation of its respective articles of incorporation, bylaws or other similar constitutive document, each as amended, or (ii) in default in the performance or observance of any obligation, agreement, covenant or condition contained in any contract, indenture, mortgage, deed of trust, loan or credit agreement, note, lease or other agreement or instrument to which the Company or any of its consolidated subsidiaries is a party or by which it or any of them may be bound, or to which any of the property or assets of the Company or any of its consolidated subsidiaries is subject (collectively, “Agreements and Instruments”), except for any such default with respect to this clause (ii) that would not result in a Material Adverse Effect; and the execution, delivery and performance of each of the Transaction Documents, the consummation of the transactions contemplated herein and in the Registration Statement, the General Disclosure Package and the Prospectus (including the issuance and sale of the Securities and the use of the proceeds from the sale of the Securities as described in the General Disclosure Package and the Prospectus under the caption “Use of Proceeds”), and compliance by the Company with its obligations hereunder and under the Indenture and the Securities have been duly authorized by all necessary corporate action

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and do not and will not, whether with or without the giving of notice or passage of time or both, conflict with or constitute a breach of, or default or a Repayment Event (as defined below) under, or result in the creation or imposition of any lien, charge or encumbrance upon any property or assets of the Company or any of its consolidated subsidiaries pursuant to, the Agreements and Instruments except for such conflicts, breaches or defaults or liens, charges or encumbrances that, singly or in the aggregate, would not result in a Material Adverse Effect, nor will such action result in any violation of the provisions of (A) the articles of incorporation, bylaws or other similar constitutive document, each as amended, of the Company or any of its consolidated subsidiaries, or (B) any applicable law, statute, rule, regulation, judgment, order, writ or decree of any government, government instrumentality or court, domestic or foreign, having jurisdiction over the Company or any of its consolidated subsidiaries or any of their assets, properties or operations, except for any such violations with respect to this clause (B) as would not, individually or in the aggregate, result in a Material Adverse Effect. As used herein, a “Repayment Event” means any event or condition which gives the holder of any note, debenture or other evidence of indebtedness (or any person acting on such holder’s behalf) the right to require the repurchase, redemption or repayment of all or a portion of such indebtedness by the Company or any of its consolidated subsidiaries.

(p)Absence of Further Requirements. No filing with, or authorization, approval, consent, license, order, registration, qualification or decree of, any court or governmental authority or agency is necessary or required for the performance by the Company of its obligations under each of the Transaction Documents, in connection with the offering, issuance or sale of the Securities hereunder or the consummation of the transactions contemplated by the Transaction Documents or for the due execution and delivery of the Indenture and the Securities by the Company, except such as have been already obtained, and such as may be required under state securities laws.

(q)Labor Matters. No labor dispute with the employees of the Company or any of its consolidated subsidiaries exists or, to the knowledge of the Company, is imminent, and the Company is not aware of any existing or imminent labor disturbance by the employees of any of its or any of its consolidated subsidiaries’ respective principal suppliers, manufacturers, customers or contractors, which, in either case, would reasonably be expected to result in a Material Adverse Effect.

(r)Intellectual Property Rights. Except as set forth in the General Disclosure Package and the Prospectus, to the best of the Company’s knowledge, the Company or its subsidiaries own or possess a valid right to use all patents, trademarks, service marks, trade names, copyrights, patentable inventions, trade secret, know-how and other intellectual property (collectively, the “Intellectual Property”) used by the Company or its subsidiaries in, and material to, the conduct of the Company’s or its subsidiaries’ business as now conducted or as proposed in the General Disclosure Package and the Prospectus to be conducted. Except as set forth in the General Disclosure Package and the Prospectus, there is no material infringement by third parties of any of the Company’s Intellectual Property and there are no legal or governmental actions, suits, proceedings or claims pending or, to the best of the Company’s knowledge, threatened, against the Company (i) challenging the Company’s rights in or to any Intellectual Property, (ii) challenging the validity or scope of any Intellectual Property owned by the Company, or (iii) alleging that the operation of the Company’s business as now conducted infringes or otherwise violates any patent,

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trademark, copyright, trade secret or other proprietary rights of a third party, and the Company is unaware of any facts which would form a reasonable basis for any such claim.

(s)Absence of Proceedings. Except as disclosed in the Registration Statement, the General Disclosure Package and the Prospectus, there is no action, suit, proceeding, inquiry or investigation before or brought by any court or governmental agency or body, domestic or foreign, now pending, or, to the knowledge of the Company, threatened, against or affecting the Company or any of its consolidated subsidiaries which would reasonably be expected to result in a Material Adverse Effect, or which would reasonably be expected to materially and adversely affect (i) the properties or assets of the Company and its consolidated subsidiaries or (ii) the consummation of the transactions contemplated by the Transaction Documents or the performance by the Company of its obligations hereunder or thereunder. The aggregate of all pending legal or governmental proceedings to which the Company or any of its consolidated subsidiaries is a party or of which any of their respective property or assets is the subject which are not described in the General Disclosure Package and the Prospectus, including ordinary routine litigation incidental to the business of the Company and its consolidated subsidiaries, would not reasonably be expected to result in a Material Adverse Effect. The Registration Statement is not the subject of a pending proceeding or examination under Section 8(d) or 8(e) of the 1933 Act, and the Company is not the subject of a pending proceeding under Section 8A of the 1933 Act in connection with the offering of the Securities.

(t)Accuracy of Exhibits. There are no contracts or documents which are required to be described in the Registration Statement, the General Disclosure Package, the Prospectus or the documents incorporated by reference therein or to be filed as exhibits thereto which have not been so described and filed as required except that this Agreement, an opinion of Perkins Coie LLP with respect to the validity of the Securities and the Supplemental Indenture establishing the form and the terms of the Securities will be filed as exhibits to a Current Report on Form 8-K which shall be filed with the Commission in accordance with the 1934 Act and the 1934 Act Regulations.

(u)Title to Property. The Company and its consolidated subsidiaries have good and marketable title to all real property owned by the Company and its consolidated subsidiaries and good title to all other properties owned by them, in each case free and clear of all mortgages, pledges, liens, security interests, claims, restrictions or encumbrances of any kind except such as (i) are described in the Registration Statement, the General Disclosure Package and the Prospectus or (ii) do not, singly or in the aggregate, materially affect the value of such property and do not interfere with the use made and proposed to be made of such property by the Company or any of its consolidated subsidiaries; and all of the leases and subleases material to the business of the Company and its consolidated subsidiaries, considered as one enterprise, and under which the Company or any of its consolidated subsidiaries holds properties described in the Registration Statement, the General Disclosure Package and the Prospectus are in full force and effect, and neither the Company nor any of its consolidated subsidiaries has any notice of any claim of any sort that has been asserted by anyone adverse to the rights of the Company or any of its consolidated subsidiaries under any of the leases or subleases mentioned above, or affecting or questioning the rights of the Company or any of its consolidated subsidiaries to the continued possession of the leased or subleased premises under any such lease or sublease, except where such would not have a Material Adverse Effect.

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(v)Investment Company Act. The Company has been advised of the rules and requirements under the Investment Company Act of 1940 (as amended, and the rules and regulations promulgated thereunder, the “Investment Company Act”). The Company is not, and after giving effect to the offering and sale of the Securities, the receipt of payment for the Securities and the application of the proceeds thereof as contemplated under the caption “Use of Proceeds” in the Registration Statement, the General Disclosure Package and the Prospectus will not be, required to register as an “investment company” within the meaning of the Investment Company Act.

(w)Tax Law Compliance. The Company and its consolidated subsidiaries have paid all federal, state, local and foreign taxes (other than those (i) that are being contested in good faith and for which adequate reserves have been established in accordance with GAAP or (ii) that, if not paid, would not have a Material Adverse Effect) and filed (or obtained extensions with respect to) all tax returns required to be paid or filed; and except as otherwise disclosed in the Registration Statement, the General Disclosure Package and the Prospectus, there is no tax deficiency that has been, or could reasonably be expected to be, asserted against the Company or any of its consolidated subsidiaries or any of their respective properties or assets that would have a Material Adverse Effect.

(x)Possession of Licenses and Permits. The Company and its consolidated subsidiaries possess such permits, licenses, approvals, consents and other authorizations (collectively, “Governmental Licenses”) issued by the appropriate federal, state, local or foreign governmental or regulatory agencies or bodies necessary to conduct the businesses now operated by them in the manner described in the Registration Statement, the General Disclosure Package and the Prospectus, except where the failure to possess any such Governmental Licenses would not have a Material Adverse Effect. The Company and its consolidated subsidiaries are in compliance with the terms and conditions of all such Governmental Licenses, except where the failure to so possess or comply would not, singly or in the aggregate, have a Material Adverse Effect. All of the Governmental Licenses are valid and in full force and effect, except where the invalidity of such Governmental Licenses or the failure of such Governmental Licenses to be in full force and effect would not have a Material Adverse Effect; and neither the Company nor any of its consolidated subsidiaries has received any notice of proceedings related to the revocation or modification of any such Governmental Licenses which, singly or in the aggregate, if the subject of an unfavorable decision, ruling or finding, would result in a Material Adverse Effect.

(y)Compliance with Environmental Laws. Except as disclosed in the Registration Statement, the General Disclosure Package and the Prospectus and except as would not, singly or in the aggregate, result in a Material Adverse Effect, (i) neither the Company nor any of its consolidated subsidiaries is in violation of any federal, state, local or foreign statute, law, rule, regulation, ordinance, code, policy or rule of common law or any judicial or administrative interpretation thereof, including any judicial or administrative order, consent, decree or judgment, relating to pollution or protection of human health, the environment (including, without limitation, ambient air, surface water, groundwater, land surface or subsurface strata) or wildlife, including, without limitation, laws and regulations relating to the release or threatened release of chemicals, pollutants, contaminants, wastes, toxic substances, hazardous substances, petroleum or petroleum products (collectively, “Hazardous Materials”) or to the manufacture, processing, distribution, use, treatment, storage, disposal, transport or handling of Hazardous Materials (collectively,

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“Environmental Laws”); (ii) the Company and its consolidated subsidiaries have all permits, authorizations and approvals required under any applicable Environmental Laws and are each in compliance with their requirements; (iii) there are no pending or, to the knowledge of the Company, threatened administrative, regulatory or judicial actions, suits, demands, demand letters, claims, liens, notices of noncompliance or violation, investigations or proceedings relating to any Environmental Laws against the Company or any of its consolidated subsidiaries; and (iv) there are no events or circumstances that might reasonably be expected to form the basis of an order for clean-up or remediation, or an action, suit or proceeding by any private party or governmental body or agency, against or affecting the Company or any of its consolidated subsidiaries relating to Hazardous Materials or any Environmental Laws.

(z)Periodic Review of Costs of Environmental Compliance. In the ordinary course of its business, the Company conducts a periodic review of the effect of Environmental Laws on the business, operations and properties of the Company and its subsidiaries, in the course of which it identifies and evaluates associated costs and liabilities (including, without limitation, any capital or operating expenditures required for clean-up, closure of properties or compliance with Environmental Laws or any permit, license or approval, any related constraints on operating activities and any potential liabilities to third parties). On the basis of such review and the amount of its established reserves, the Company has reasonably concluded that such associated costs and liabilities would not, individually or in the aggregate, be expected to have a Material Adverse Effect.

(aa) ERISA Compliance. Except for noncompliance that could not reasonably be expected to result in a Material Adverse Effect, (i) each employee benefit plan, within the meaning of Section 3(3) of the Employee Retirement Income Security Act of 1974, as amended (“ERISA”), for which the Company or any member of its “Controlled Group” (defined as any organization which is a member of a controlled group of corporations within the meaning of Section 414 of the of the Internal Revenue Code of 1986, as amended (the “Code”) would have any liability) (each, a “Plan”) has been maintained in compliance with its terms and the requirements of any applicable statutes, orders, rules and regulations, including but not limited to ERISA and the Code; (ii) no prohibited transaction, within the meaning of Section 406 of ERISA or Section 4975 of the Code, has occurred with respect to any Plan excluding transactions effected pursuant to a statutory or administrative exemption; (iii) for each Plan that is subject to the funding rules of Section 412 of the Code or Section 302 of ERISA, the minimum funding standard of Section 412 of the Code or Section 302 of ERISA, as applicable, has been satisfied (without taking into account any waiver thereof or extension of any amortization period) and is reasonably expected to be satisfied in the future (without taking into account any waiver thereof or extension of any amortization period); (iv) the fair value of the assets of each Plan and the benefit obligations accrued under such Plan have been properly accounted for in accordance with GAAP on the financial statements of the Company and its consolidated subsidiaries; (v) no “reportable event” (within the meaning of Section 4043(c) of ERISA) has occurred or is reasonably expected to occur; (vi) neither the Company nor any member of its Controlled Group has incurred, nor reasonably expects to incur, any liability under Title IV of ERISA (other than contributions to the Plan or premiums to the Pension Benefit Guaranty Corporation (“PBGC”), in the ordinary course and without default) in respect of a Plan (including a “multiemployer plan”, within the meaning of Section 4001(a)(3) of ERISA); and (vii) there is no pending audit or investigation by the Internal Revenue Service, the U.S. Department of Labor, the

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PBGC or any other governmental agency or any foreign regulatory agency with respect to any Plan. To the knowledge of the Company, none of the following events has occurred or is reasonably likely to occur: (A) a material increase in the aggregate amount of contributions required to be made to all Plans by the Company or its consolidated subsidiaries in the current fiscal year of the Company and its consolidated subsidiaries compared to the amount of such contributions made in the Company and its consolidated subsidiaries’ most recently completed fiscal year; or (B) a material increase in the Company and its consolidated subsidiaries’ “accumulated post-retirement benefit obligations” (within the meaning of Statement of Financial Accounting Standards 106) compared to the amount of such obligations in the Company and its consolidated subsidiaries’ most recently completed fiscal year.

(bb) Internal Controls and Disclosure Controls. The Company maintains a system of internal accounting controls over financial reporting (as such term is defined in Rule 13a-15(f) under the 1934 Act) sufficient to provide reasonable assurance that (i) transactions are executed in accordance with management’s general or specific authorizations; (ii) transactions are recorded as necessary to permit preparation of financial statements in conformity with GAAP and to maintain accountability for assets; (iii) access to assets is permitted only in accordance with management’s general or specific authorization; (iv) the recorded accountability for assets is compared with the existing assets at reasonable intervals and appropriate action is taken with respect to any differences; and (v) the interactive data in XBRL included or incorporated by reference in the Registration Statement, the Statutory Prospectus and the Prospectus fairly presents the information called for in all material respects and is prepared in accordance with the Commission’s rules and guidelines applicable thereto. Except as disclosed in the General Disclosure Package and the Prospectus, since the end of the Company’s most recent audited fiscal year, there has been no material weakness or significant deficiencies in the Company’s internal control over financial reporting (whether or not remediated) and no change in the Company’s internal control over financial reporting that has materially affected, or is reasonably likely to materially affect, the Company’s internal control over financial reporting.

The Company employs disclosure controls and procedures that are designed to ensure that information required to be disclosed by the Company in the reports that it files or submits under the 1934 Act is recorded, processed, summarized and reported, within the time periods specified in the Commission’s rules and forms, and is accumulated and communicated to the Company’s management, including its principal executive officer or officers and principal financial officer or officers, as appropriate, to allow timely decisions regarding disclosure.

(cc) Sarbanes-Oxley Compliance. There is and has been no failure on the part of the Company and any of its directors or officers, in their capacities as such, to comply with any provision of the Sarbanes-Oxley Act of 2002 and the rules and regulations promulgated in connection therewith (the “Sarbanes-Oxley Act”), including Section 402 thereof related to loans and Section 302 and Section 906 thereof related to certifications.

(dd) Insurance. The Company and its consolidated subsidiaries have insurance covering their respective properties, operations, personnel and businesses, which insurance is in amounts and insures against such losses and risks as are adequate to protect the Company and its consolidated

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subsidiaries and their respective businesses; and neither the Company nor any of its consolidated subsidiaries has (i) received notice from any insurer or agent of such insurer that capital improvements or other expenditures are required or necessary to be made in order to continue such insurance, or (ii) any reason to believe that it will not be able to renew its existing insurance coverage as and when such coverage expires or to obtain similar coverage at reasonable cost from similar insurers as may be necessary to continue its business.

(ee) Cybersecurity. To the knowledge of the Company, there has been no material security breach, unauthorized use of or access to, or other material compromise of any of the Company’s or its’ subsidiaries’ information technology and computer systems, networks, hardware, software, data and databases (including the data and information of their respective customers, employees, suppliers, vendors and any third party data maintained, processed or stored by the Company and its subsidiaries, and any such data processed or stored by third parties on behalf of them), equipment or technology (collectively, “IT Systems and Data”). Neither the Company nor its subsidiaries have been notified of, and neither of them have knowledge of any event or condition that would reasonably be expected to result in, any material security breach, unauthorized use of or access to, or other material compromise to their IT Systems and Data. The Company and its subsidiaries are presently in compliance in all material respects with all applicable laws or statutes and all judgments, orders, rules and regulations of any court or arbitrator or governmental or regulatory authority, internal policies and contractual obligations relating to the privacy and security of IT Systems and Data and to the protection of such IT Systems and Data from unauthorized use, access, misappropriation or modification. The Company and its subsidiaries have implemented commercially reasonable controls, policies, procedures, and technological safeguards to maintain and protect the integrity, continuous operation, redundancy and security of their IT Systems and Data and have implemented backup and disaster recovery technology reasonably consistent with industry standards and practices, or as required by applicable regulatory standards, and comply with such controls, policies, procedures, and technological safeguards in all material respects.

(ff) No Unlawful Contributions or Other Payments. None of the Company, any of its subsidiaries or, to the best of the Company’s knowledge, any director, officer, agent, employee, affiliate or other person acting on behalf of the Company or any of its subsidiaries is aware of or has taken any action, directly or indirectly, that would result in a violation by such persons of (i) the Foreign Corrupt Practices Act of 1977, as amended, and the rules and regulations thereunder (the “FCPA”), including, without limitation, making use of the mails or any means or instrumentality of interstate commerce corruptly in furtherance of an offer, payment, promise to pay or authorization of the payment of any money, or other property, gift, promise to give, or authorization of the giving of anything of value to any “foreign official” (as such term is defined in the FCPA) or any foreign political party or official thereof or any candidate for foreign political office, in contravention of the FCPA, (ii) the U.K. Bribery Act 2010 (the “Bribery Act”), or (iii) other applicable anti-corruption regimes, and the Company, its subsidiaries and, to the best of the Company’s knowledge, its affiliates have conducted their businesses in compliance with the FCPA and the Bribery Act and have instituted and maintain policies and procedures designed to ensure, and which are reasonably expected to continue to ensure, continued compliance therewith. None of the Company, any of its subsidiaries or, to the best of the Company’s knowledge, any director, officer, agent, employee, affiliate or other person acting on behalf of the Company or its subsidiaries will use any part of the

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proceeds from the sale of the Securities, directly or indirectly, in violation of the FCPA or the rules or regulations thereunder.

(gg) No Conflict with Anti-Money Laundering Laws. The operations of the Company and its subsidiaries are and have been conducted at all times in compliance with applicable financial recordkeeping and reporting requirements, including those of the Currency and Foreign Transactions Reporting Act of 1970, as amended, the applicable money laundering statutes of all jurisdictions where the Company or any of its consolidated subsidiaries conduct business, the rules and regulations thereunder and any related or similar rules, regulations or guidelines issued, administered or enforced by any governmental agency (collectively, the “Anti-Money Laundering Laws”) and no action, suit or proceeding by or before any court or governmental agency, authority or body or any arbitrator involving the Company or any of its subsidiaries with respect to the Anti-Money Laundering Laws is pending or, to the best of the Company’s knowledge, threatened.

(hh) No Conflict with OFAC Laws. Neither the Company nor any of its subsidiaries nor, to the knowledge of the Company, any director, officer, agent, employee, affiliate or other person acting on behalf of the Company or any of its subsidiaries (i) is, or is controlled or 50% or more owned by or is acting on behalf of, an individual or entity that is, currently the subject or the target of any sanctions administered or enforced by the United States (including any administered or enforced by the Office of Foreign Assets Control of the U.S. Department of the Treasury, the U.S. Department of State or the Bureau of Industry and Security of the U.S. Department of Commerce), the United Nations Security Council, the European Union, the United Kingdom (including sanctions administered or enforced by His Majesty’s Treasury) or other relevant sanctions authority (collectively, “Sanctions”), (ii) is located, organized or resident in a country or territory that is, or whose government is, currently the subject or the target of Sanctions that broadly prohibit dealings with that country or territory (the “Sanctioned Countries”), or (iii) will, directly or indirectly, use the proceeds of this offering, or lend, contribute or otherwise make available such proceeds to any subsidiary, joint venture partner or other individual or entity (x) to fund or facilitate any activities of or business with any person that, at the time of such funding or facilitation, is the subject or the target of Sanctions; (y) to fund or facilitate any activities of or business in any Sanctioned Country; or (z) in any other manner that would result in a violation of any Sanctions by, or could result in the imposition of Sanctions against, any individual or entity (including any individual or entity participating in the offering, whether as underwriter, advisor, investor or otherwise). The Company and its subsidiaries (as of the date hereof) have not knowingly engaged in, are not now knowingly engaged in and will not knowingly engage in any dealings or transactions with any person that at the time of the dealing or transaction is or was the subject or the target of Sanctions or with any of the Sanctioned Countries, in each case if such dealing or transaction is prohibited by law.

(ii) No Price Stabilization or Manipulation. Neither the Company nor any of its consolidated subsidiaries or affiliates has taken nor will the Company or any of its consolidated subsidiaries or affiliates take, directly or indirectly, any action which is designed to or which has constituted or which would reasonably be expected to cause or result in the stabilization or manipulation of the price of any security of the Company to facilitate the sale or resale of the Securities.

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(jj) Subsidiary Dividends. Except for applicable regulatory limitations on dividend payments, as disclosed in the General Disclosure Package and the Prospectus, no consolidated subsidiary of the Company is currently prohibited, directly or indirectly, under any agreement or other instrument to which it is a party or is subject, from paying any dividends to the Company, from making any other distribution on such subsidiary’s capital stock or from repaying to the Company any loans or advances to such subsidiary from the Company.

(kk) Related Party Transactions. There are no business relationships or related-party transactions involving the Company or any of its subsidiaries or any other person required to be described in the Registration Statement, the General Disclosure Package and the Prospectus that have not been described as required.

(ll) Agency Fee. Neither the Company nor any of its consolidated subsidiaries is a party to any contract, agreement or understanding with any person (other than this Agreement) that would give rise to a valid claim against the Company or any of its consolidated subsidiaries or the Underwriters for a brokerage commission, finder’s fee or like payment in connection with the offering and sale of the Securities.

(mm) Regulation T, U or X. The application of the proceeds received by the Company from the issuance, sale and delivery of the Securities as described in the Registration Statement, the General Disclosure Package and the Prospectus will not violate Regulation T, U or X of the Board of Governors of the Federal Reserve System or any other regulation of such Board of Governors.

(nn) Reliable Sources. Nothing has come to the attention of the Company that has caused the Company to believe that the statistical and market-related data included in the Registration Statement, the General Disclosure Package and the Prospectus is not based on or derived from sources that are reliable and accurate in all material respects.

(oo) Officers’ Certificates. Any certificate signed by an officer of the Company and delivered to the Representatives or to counsel for the Underwriters shall be deemed to be a representation and warranty by the Company to each Underwriter as to the matters set forth therein.

SECTION 2. Sale and Delivery to Underwriters; Closing.

(a)The Securities. On the basis of the representations, warranties and agreements herein contained and subject to the terms and conditions herein set forth, the Company agrees to sell to each Underwriter, severally and not jointly, and each Underwriter, severally and not jointly, agrees to purchase from the Company, at a purchase price of 99.000% of the principal amount thereof, the aggregate principal amount of Securities set forth in Schedule A hereto opposite the name of such Underwriter, plus any additional principal amount of Securities which such Underwriter may become obligated to purchase pursuant to the provisions of Section 10 hereof.

(b)Payment. Payment of the purchase price for, and delivery of certificates for, the Securities shall be made at the offices of the Company at 4902 North Biltmore Lane, Madison, Wisconsin, 53718, or at such other place as shall be agreed upon by the Representatives and the Company, at 10:00 a.m. (New York City time) on the third business day after the date hereof (unless

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postponed in accordance with the provisions of Section 10 hereof), or such other time not later than ten business days after such date as shall be agreed upon by the Representatives and the Company (such time and date of payment and delivery being herein called the “Closing Time”). Payment shall be made to the Company by wire transfer of immediately available funds to a bank account designated by the Company, against delivery to the Representatives for the respective accounts of the Underwriters of certificates for the Securities to be purchased by them. It is understood that each Underwriter has authorized the Representatives, for its account, to accept delivery of, receipt for, and make payment of the purchase price for, the Securities that it has agreed to purchase.

(c)Denominations; Registration. Certificates for the Securities shall be in such denominations (in integral multiples of $1,000) as the Representatives may request in writing at least two full business days before the Closing Time and registered in the name of Cede & Co., as nominee of DTC. The certificates for the Securities will be made available for examination and packaging by the Representatives in New York, New York not later than noon (New York City time) on the last business day prior to the Closing Time.

SECTION 3. Covenants of the Company. The Company covenants and agrees with each Underwriter as follows:

(a)Compliance with Securities Regulations and Commission Requests. The Company, subject to Section 3(b) hereof, will notify the Representatives immediately and confirm the notice in writing, (i) when any post-effective amendment to the Registration Statement shall become effective, or any supplement to the Prospectus or any amended Prospectus shall have been filed, (ii) of the receipt of any comments from the Commission with respect to the Registration Statement, (iii) of any request by the Commission for any amendment to the Registration Statement or any amendment or supplement to the Prospectus or for additional information, (iv) of the issuance by the Commission of any stop order suspending the effectiveness of the Registration Statement or of any order preventing or suspending the use of any preliminary prospectus, or of the suspension of the qualification of the Securities for offering or sale in any jurisdiction, or of the initiation or threatening of any proceedings for any of such purposes or of any examination pursuant to Section 8(e) of the 1933 Act concerning the Registration Statement, and (v) if the Company becomes the subject of a proceeding under Section 8A of the 1933 Act in connection with the offering of the Securities. The Company will effect the filings required under Rule 424(b), in the manner and within the time period required by Rule 424(b) (without reliance on Rule 424(b)(8)), and will take such steps as it deems necessary to ascertain promptly whether the form of prospectus transmitted for filing under Rule 424(b) was received for filing by the Commission and, in the event that it was not, it will promptly file such prospectus. The Company will make every reasonable effort to prevent the issuance of any stop order and, if any stop order is issued, to obtain the lifting thereof at the earliest possible moment.

(b)Filing of Amendments. The Company will give the Representatives notice of its intention to file or prepare any amendment, supplement or revision to the Registration Statement, preliminary prospectus or Prospectus if such amendment, supplement or revision relates to either any preliminary prospectus in connection with the offering of the Securities (including any prospectus included in the Registration Statement at the time it became effective) or to the Prospectus, whether

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pursuant to the 1933 Act, the 1934 Act or otherwise and will furnish the Representatives with copies of any such documents a reasonable amount of time prior to such proposed filing or use, as the case may be, and will not file or use any such document to which the Representatives or counsel for the Underwriters shall reasonably object.

(c)Delivery of Registration Statements. The Company has furnished or will deliver to the Representatives and counsel for the Underwriters, without charge, copies of the Registration Statement and of each amendment thereto (including exhibits filed therewith or incorporated by reference therein and documents incorporated or deemed to be incorporated by reference therein) and copies of all consents and certificates of experts, and will also deliver to the Representatives, without charge, a conformed copy of the Registration Statement and of each amendment thereto (without exhibits) for each of the Underwriters. The copies of the Registration Statement and each amendment thereto furnished to the Underwriters will be identical to the electronically transmitted copies thereof filed with the Commission pursuant to EDGAR, except to the extent permitted by Regulation S-T.

(d)Delivery of Prospectuses. The Company has delivered or will deliver to each Underwriter, without charge, as many copies of the final prospectus as such Underwriter reasonably requested, and the Company hereby consents to the use of such copies for purposes permitted by the 1933 Act. The Company will furnish to each Underwriter, without charge, during the period when the Prospectus is required to be delivered under the 1933 Act or the 1934 Act (the “Prospectus Delivery Period”), such number of copies of the Prospectus (as amended or supplemented) as such Underwriter may reasonably request. The Prospectus and any amendments or supplements thereto furnished to the Underwriters will be identical to the electronically transmitted copies thereof filed with the Commission pursuant to EDGAR, except to the extent permitted by Regulation S T.

(e)Continued Compliance with Securities Laws. The Company will comply with the 1933 Act and the 1933 Act Regulations and the 1934 Act and the 1934 Act Regulations and the 1939 Act and the 1939 Act Regulations so as to permit the completion of the distribution of the Securities as contemplated in this Agreement and in the Prospectus. If at any time when a prospectus is required by the 1933 Act to be delivered in connection with sales of the Securities, any event shall occur or condition shall exist as a result of which it is necessary, in the reasonable opinion of counsel for the Underwriters or for the Company, to amend the Registration Statement or amend or supplement the Prospectus in order that the Registration Statement or the Prospectus will not include any untrue statements of a material fact or omit to state a material fact necessary in order to make the statements therein not misleading in the light of the circumstances existing at the time it is delivered to a purchaser, or if it shall be necessary, in the reasonable opinion of such counsel, at any such time to amend the Registration Statement or amend or supplement the Prospectus in order to comply with the requirements of the 1933 Act or the 1933 Act Regulations, the Company will promptly prepare and file with the Commission, subject to Section 3(b) hereof, such amendment or supplement as may be necessary to correct such statement or omission or to make the Registration Statement or the Prospectus comply with such requirements, and the Company will furnish to the Underwriters such number of copies of such amendment or supplement as the Underwriters may reasonably request.

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(f)Blue Sky Qualifications. The Company will use its best efforts, in cooperation with the Underwriters, to qualify the Securities for offering and sale under the applicable securities laws of such states and other jurisdictions as the Representatives may designate and to maintain such qualifications in effect so long as required for the sale of the Securities; provided, however, that the Company shall not be obligated to file any general consent to service of process or to qualify as a foreign corporation or as a dealer in securities in any jurisdiction in which it is not so qualified or to subject itself to taxation in respect of doing business in any jurisdiction in which it is not otherwise so subject. In each jurisdiction in which the Securities have been so qualified, the Company will file such statements and reports as may be required by the laws of such jurisdiction to continue such qualification in effect for such period.

(g)Rule 158. The Company will timely file such reports pursuant to the 1934 Act as are necessary in order to make generally available to its securityholders as soon as practicable an earnings statement for the purposes of, and to provide the benefits contemplated by, the last paragraph of Section 11(a) of the 1933 Act.

(h)Use of Proceeds. The Company will use the net proceeds received by it from the sale of the Securities in the manner specified in the General Disclosure Package and the Prospectus under the caption “Use of Proceeds.”

(i)Restriction on Sale of Securities. From the date of the Prospectus until the Closing Time, the Company will not, without the prior written consent of the Representatives, (i) directly or indirectly, offer, pledge, sell, contract to sell, sell any option or contract to purchase, purchase any option or contract to sell, grant any option, right or warrant to purchase or otherwise transfer or dispose of any debt securities of the Company or any securities convertible into or exercisable or exchangeable for debt securities of the Company or file any registration statement under the 1933 Act with respect to any of the foregoing, or (ii) enter into any swap or any other agreement or any transaction that transfers, in whole or in part, directly or indirectly, the economic consequence of ownership of debt securities of the Company, whether any such swap or transaction described in clause (i) or (ii) above is to be settled by delivery of debt securities of the Company or such other securities, in cash or otherwise. The foregoing sentence shall not apply to the Securities to be sold hereunder.

(j)Reporting Requirements. The Company, during the period when the Prospectus is required to be delivered under the 1933 Act or the 1934 Act, will file all documents required to be filed with the Commission pursuant to the 1934 Act within the time periods required by the 1934 Act and the 1934 Act Regulations.

(k)Compliance with Sarbanes-Oxley Act. The Company will comply with all applicable securities and other laws, rules and regulations, including, without limitation, the Sarbanes-Oxley Act, and use its best efforts to cause the Company’s directors and officers, in their capacities as such, to comply with such laws, rules and regulations, including, without limitation, the provisions of the Sarbanes-Oxley Act.

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(l)2005 Act Filings. The Company shall timely file all notifications, forms and reports that may be required under the 2005 Act so as to permit the completion of the distribution and sale of the Securities as contemplated in this Agreement and in the Prospectus.

(m)Rating of Securities. The Company shall take all reasonable action necessary to enable Standard & Poor’s Ratings Services, a division of McGraw Hill, Inc. (“S&P”), and Moody’s Investors Service Inc. (“Moody’s”) to provide their respective credit ratings of the Securities.

(n)DTC. The Company will cooperate with the Representatives and use its best efforts to permit the Securities to be eligible for clearance and settlement through the facilities of DTC.

(o)Issuer Free Writing Prospectus. The Company represents and agrees that, unless it obtains the prior consent of the Representatives, and each Underwriter represents and agrees that, unless it obtains the prior consent of the Company and the Representatives, it has not made and will not make any offer relating to the Securities that would constitute an “issuer free writing prospectus,” as defined in Rule 433, or that would otherwise constitute a “free writing prospectus,” as defined in Rule 405, required to be filed with the Commission. Any such free writing prospectus consented to by the Company and the Representatives is hereinafter referred to as a “Permitted Free Writing Prospectus.” The Company represents that it has treated or agrees that it will treat each Permitted Free Writing Prospectus as an “issuer free writing prospectus,” as defined in Rule 433, and has complied and will comply with the requirements of Rule 433 applicable to any Permitted Free Writing Prospectus, including timely filing with the Commission where required, legending and record keeping.

(p)Final Term Sheet. The Company will prepare a final term sheet containing only a description of the Securities, in a form attached hereto as Schedule C and approved by the Representatives, and will file such term sheet pursuant to Rule 433(d) of the 1933 Act Regulations within the time required by such rule (such term sheet, the “Final Term Sheet”). The Final Term Sheet is an Issuer Free Writing Prospectus for purposes of this Agreement.

(q)Notice of Inability to Use Automatic Shelf Registration Statement Form. If, at any time during the Prospectus Delivery Period, the Company receives from the Commission a notice pursuant to Rule 401(g)(2) or otherwise ceases to be eligible to use the automatic shelf registration statement form, the Company will (i) promptly notify the Representatives, (ii) promptly file a new registration statement or post-effective amendment on the proper form relating to the Securities, in a form satisfactory to the Representatives, (iii) use its best efforts to cause such registration statement or post-effective amendment to be declared effective, and (iv) promptly notify the Representatives of such effectiveness. The Company will take all other action necessary or appropriate to permit the public offering and sale of the Securities to continue as contemplated in the registration statement that was the subject of the Rule 401(g)(2) notice or for which the Company has otherwise become ineligible. References herein to the Registration Statement shall include such new registration statement or post-effective amendment, as the case may be.

(r)Filing Fees. The Company agrees to pay the required Commission filing fees relating to the Securities within the time required by and in accordance with Rule 456(b)(1) and Rule 457(r) of the 1933 Act Regulations.

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SECTION 4. Payment of Expenses.

(a)Expenses. The Company will pay all costs, fees and expenses incident to the performance of its obligations under and in connection with the transactions contemplated by this Agreement, including, without limitation (i) the preparation, printing and filing of the Registration Statement (including financial statements and any schedules or exhibits and any document incorporated therein by reference) and of each amendment or supplement thereto, (ii) the reproduction and delivery to the Underwriters of any Transaction Document, any agreement among the Underwriters and such other documents as may be required in connection with the offering, purchase, sale, issuance or delivery of the Securities, (iii) the preparation, issuance and delivery of the certificates for the Securities to the Underwriters, including any transfer taxes and any stamp or other duties payable upon the sale, issuance or delivery of the Securities to the Underwriters and any charges of DTC in connection therewith, (iv) the fees and disbursements of the Company’s counsel, accountants and other advisors, (v) the qualification of the Securities under securities laws in accordance with the provisions of Section 3(f) hereof, including filing fees and the reasonable fees and disbursements of counsel for the Underwriters in connection therewith and in connection with the preparation of the Blue Sky Survey and any supplement thereto, (vi) the printing and delivery to the Underwriters of copies of each Issuer Free Writing Prospectus, each preliminary prospectus and the Prospectus and any amendments or supplements thereto, (vii) the fees and expenses of the Trustee, including the fees and disbursements of counsel for the Trustee in connection with the Indenture and the Securities, and (viii) any fees payable in connection with the rating of the Securities.

(b)Termination of Agreement. If this Agreement is terminated by the Representatives in accordance with the provisions of Section 5, Section 9, or Section 10 hereof, including if the sale to the Underwriters of the Securities on the Closing Time is not consummated because of any refusal, inability or failure on the part of the Company to perform any agreement herein or to comply with any provision hereof, the Company shall reimburse the Underwriters for all of their out-of-pocket expenses, including reasonable fees and disbursements of counsel for the Underwriters, printing expenses, travel expenses, postage, facsimile and telephone charges.

SECTION 5. Conditions of Underwriters’ Obligations. The obligations of the several Underwriters hereunder are subject to the accuracy in all material respects of the representations and warranties of the Company contained in Section 1 hereof or in certificates of any officer of the Company or any subsidiary of the Company delivered pursuant to the provisions hereof, to the performance in all material respects by the Company of its covenants and other obligations hereunder, and to the following further conditions:

(a)Effectiveness of Registration Statement. The Registration Statement has become effective under the 1933 Act upon filing with the Commission and, at the Closing Time, no stop order suspending the effectiveness of the Registration Statement shall have been issued under the 1933 Act or proceedings therefor initiated or threatened by the Commission, and any request on the part of the Commission for additional information shall have been complied with to the reasonable satisfaction of counsel to the Underwriters. A prospectus containing the Rule 430B Information

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shall have been filed with the Commission in accordance with Rule 424(b) without reliance on Rule 424(b)(8).

(b)Opinion of Counsel for Company. At the Closing Time, the Representatives shall have received the opinion, dated as of the Closing Time, of Perkins Coie LLP, counsel for the Company, in form and substance reasonably satisfactory to counsel for the Underwriters, together with signed or reproduced copies of such letter for each of the other Underwriters, in the form previously agreed to by the parties. In rendering such opinions, each such counsel may rely as to matters of fact (but not as to legal conclusions), to the extent it deems proper, on certificates of responsible officers of the Company and its subsidiaries and of public officials.

(c)Letter from Counsel for Company. At the Closing Time, the Representatives shall have received a disclosure letter, dated as of the Closing Time, of Perkins Coie LLP, counsel for the Company, in form and substance reasonably satisfactory to counsel for the Underwriters, together with signed or reproduced copies of such letter for each of the other Underwriters, in the form previously agreed to by the parties.

(d)Opinion of Counsel for Underwriters. At the Closing Time, the Representatives shall have received the opinion, dated as of the Closing Time, of Gibson, Dunn & Crutcher LLP, counsel for the Underwriters, together with signed or reproduced copies of such letter for each of the other Underwriters. In giving such opinion such counsel may rely, as to all matters governed by the laws of jurisdictions other than the law of the State of New York, the federal law of the United States and the General Corporation Law of the State of Delaware, upon the opinions of counsel satisfactory to the Representatives. In rendering such opinion, such counsel may rely as to matters of fact (but not as to legal conclusions), to the extent they deem proper, on certificates of responsible officers of the Company and its subsidiaries and of public officials.

(e)Officers’ Certificate. At the Closing Time, there shall not have been, since the date hereof or since the respective dates as of which information is given in the General Disclosure Package, any material adverse change in the condition, financial or otherwise, in the earnings or business affairs of the Company and its subsidiaries considered as one enterprise, whether or not arising in the ordinary course of business, nor shall there have been any developments involving a prospective material adverse change of the Company and its subsidiaries considered as one enterprise, whether or not arising in the ordinary course of business, and the Representatives shall have received a certificate signed by the Chair of the Board or the Chief Executive Officer, President, an Executive Vice President or a Senior Vice President and the Chief Financial Officer, Chief Accounting Officer or Treasurer of the Company, dated as of the Closing Time, together with signed or reproduced copies of such letter for each of the other Underwriters, to the effect that (i) there has been no such material adverse change or any developments involving a prospective material adverse change, (ii) the representations and warranties in Section 1(a) hereof are true and correct with the same force and effect as though expressly made at and as of the Closing Time, (iii) the Company has complied in all material respects with all agreements and satisfied all conditions on its part to be performed or satisfied at or prior to the Closing Time, (iv) the Company is not in default in the performance of any of the covenants to be performed by it under the Indenture, and (v) no stop order suspending the effectiveness of the Registration Statement has been issued and no

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proceedings for that purpose have been instituted or are pending or, to the knowledge of the Company, are contemplated by the Commission.

(f)Accountant’s Comfort Letter. At the time of the execution of this Agreement, the Representatives shall have received from Deloitte & Touche LLP a letter dated such date, in form and substance satisfactory to the Representatives, together with signed or reproduced copies of such letter for each of the other Underwriters, containing statements and information of the type ordinarily included in accountants’ “comfort letters” to underwriters with respect to the financial statements and certain financial information contained in the Registration Statement, the General Disclosure Package and the Prospectus.

(g)Bring-down Comfort Letter. At the Closing Time, the Representatives shall have received from Deloitte & Touche LLP a letter, dated as of the Closing Time, together with signed or reproduced copies of such letter for each of the other Underwriters, to the effect that they reaffirm the statements made in the letter furnished pursuant to Section 5(f) hereof, except that the specified date referred to therein for carrying out procedures shall be a date not more than three business days prior to the Closing Time.

(h)Maintenance of Rating. At the Closing Time, the Securities shall be rated at least “Baa3” by Moody’s and “BBB-” by S&P, and the Company shall have delivered to the Representatives a letter dated the Closing Time, from each such rating agency, or other evidence satisfactory to the Representatives, confirming that the Securities have such ratings; and since the date of this Agreement, there shall not have occurred a downgrading in or withdrawal of the rating assigned to the Securities or any of the Company’s other securities by any “nationally recognized statistical rating organization,” as such term is defined in Section 3(a)(62) of the 1934 Act, and no such securities rating agency shall have publicly announced that it has under surveillance or review, with possible negative implications or a possible change that does not indicate the direction of the possible change, its rating of the Securities or any of the Company’s other securities.

(i)Indenture. The Company shall have executed and delivered the Indenture, in form and substance reasonably satisfactory to the Representatives, and the Representatives shall have received executed counterparts thereof.

(j)Additional Documents. At the Closing Time, counsel for the Underwriters shall have been furnished with such documents and opinions (including but not limited to those referenced above) as they may reasonably require for the purpose of enabling them to pass upon the issuance and sale of the Securities as herein contemplated, or in order to evidence the accuracy of any of the representations or warranties, or the fulfillment of any of the conditions, herein contained; and all proceedings taken by the Company in connection with the issuance and sale of the Securities as herein contemplated shall be reasonably satisfactory in form and substance to the Representatives and counsel for the Underwriters.

(k)Termination of Agreement. If any condition specified in this Section 5 shall not have been fulfilled when and as required to be fulfilled, this Agreement may be terminated by the Representatives by notice to the Company at any time at or prior to the Closing Time, and such termination shall be without liability of any party to any other party except as provided in Section 4

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and except that Section 1, Section 6, Section 7, Section 8, and Section 15 hereof shall survive any such termination and remain in full force and effect.

SECTION 6. Indemnification.

(a)Indemnification of the Underwriters. The Company agrees to indemnify and hold harmless each Underwriter, its affiliates, directors, officers and employees and each person, if any, who controls any Underwriter within the meaning of Section 15 of the 1933 Act or Section 20 of the 1934 Act as follows:

(i) against any and all loss, liability, claim, damage and expense whatsoever, as incurred, arising out of any untrue statement or alleged untrue statement of a material fact contained in the Registration Statement (or any amendment thereto), or the omission or alleged omission therefrom of a material fact required to be stated therein or necessary to make the statements therein not misleading or arising out of any untrue statement or alleged untrue statement of a material fact included in any preliminary prospectus, any Issuer Free Writing Prospectus or the Prospectus (or any amendment or supplement thereto), or the omission or alleged omission therefrom of a material fact necessary in order to make the statements therein, in the light of the circumstances under which they were made, not misleading;

(ii) against any and all loss, liability, claim, damage and expense whatsoever, as incurred, to the extent of the aggregate amount paid in settlement of any litigation, or any investigation or proceeding by any governmental agency or body, commenced or threatened, or of any claim whatsoever based upon any such untrue statement or omission, or any such alleged untrue statement or omission; provided that (subject to Section 6(d) hereof) any such settlement is effected with the written consent of the Company; and

(iii) against any and all expense whatsoever, as incurred (including the fees and disbursements of counsel chosen by the Representatives), reasonably incurred in investigating, preparing or defending against any litigation, or any investigation or proceeding by any governmental agency or body, commenced or threatened, or any claim whatsoever based upon any such untrue statement or omission, or any such alleged untrue statement or omission, to the extent that any such expense is not paid under clause (i) or (ii) above;

provided, however, that this indemnity agreement shall not apply to any loss, liability, claim, damage or expense to the extent arising out of any untrue statement or omission or alleged untrue statement or omission made in reliance upon and in conformity with written information furnished to the Company by any Underwriter through the Representatives expressly for use in the Registration Statement (or any amendment thereto), or any preliminary prospectus, Issuer Free Writing Prospectus or the Prospectus (or any amendment or supplement thereto), it being understood and agreed that the only such information consists of the information contained in Schedule D hereto.

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(b)Indemnification of the Company, Directors and Officers. Each Underwriter severally agrees to indemnify and hold harmless the Company, its affiliates, its directors, each of its officers who signed the Registration Statement, and each person, if any, who controls the Company within the meaning of Section 15 of the 1933 Act or Section 20 of the 1934 Act against any and all loss, liability, claim, damage and expense described in the indemnity contained in Section 6(a) hereof, as incurred, but only with respect to untrue statements or omissions, or alleged untrue statements or omissions, made in the Registration Statement (or any amendment thereto) or any preliminary prospectus, Issuer Free Writing Prospectus or the Prospectus (or any amendment or supplement thereto) in reliance upon and in conformity with written information furnished to the Company by such Underwriter through the Representatives expressly for use therein, it being understood and agreed that the only such information consists of the information contained in Schedule D hereto.

(c)Actions against Parties; Notification. Each indemnified party shall give notice as promptly as reasonably practicable to each indemnifying party of any action commenced against it in respect of which indemnity may be sought hereunder, but failure to so notify an indemnifying party shall not relieve such indemnifying party from any liability hereunder to the extent it is not materially prejudiced as a result thereof and in any event shall not relieve it from any liability which it may have otherwise than on account of this indemnity agreement. In the case of parties indemnified pursuant to Section 6(a) hereof, counsel to the indemnified parties shall be selected by the Representatives, and, in the case of parties indemnified pursuant to Section 6(b) hereof, counsel to the indemnified parties shall be selected by the Company. An indemnifying party may participate at its own expense in the defense of any such action; provided, however, that counsel to the indemnifying party shall not (except with the consent of the indemnified party) also be counsel to the indemnified party. In no event shall the indemnifying parties be liable for fees and expenses of more than one counsel (in addition to any local counsel) separate from their own counsel for all indemnified parties in connection with any one action or separate but similar or related actions in the same jurisdiction arising out of the same general allegations or circumstances. In addition, the indemnifying party shall be entitled, to the extent that it wishes, jointly with any other similarly notified indemnifying party, to assume the defense of any claim or action brought against an indemnified party with counsel reasonably satisfactory to the indemnified party. After notice from the indemnifying party to the indemnified party of its election to assume the defense of such claim or action, the indemnifying party shall not be liable to the indemnified party under this Section 6 for any legal or other expenses subsequently incurred by the indemnified party in connection with the defense thereof other than reasonable costs of investigation; provided, however, that the Representatives shall have the right to employ one counsel (in addition to local counsel) to represent them and those other Underwriters and their respective officers, employees and controlling persons who may be subject to liability arising out of any claim in respect of which indemnity may be sought by the Underwriters against the Company under this Section 6 if, in the reasonable judgment of the Representatives, either (i) there is an actual or potential conflict between the position of the Company on the one hand and the Underwriters on the other hand, or (ii) there may be defenses available to it or them that are different from or additional to those available to the Company (in any of which events the Company shall not have the right to direct the defense of such action on behalf of the Representatives with respect to such different defenses), in any of which events such reasonable fees and expenses shall be borne by the Company. No indemnifying party shall, without the prior written consent of the indemnified parties, settle or compromise or consent to the entry of

25

any judgment with respect to any litigation, or any investigation or proceeding by any governmental agency or body, commenced or threatened, or any claim whatsoever in respect of which indemnification or contribution could be sought under this Section 6 or Section 7 hereof (whether or not the indemnified parties are actual or potential parties thereto), unless such settlement, compromise or consent (A) includes an unconditional release of each indemnified party from all liability arising out of such litigation, investigation, proceeding or claim, and (B) does not include a statement as to or an admission of fault, culpability or a failure to act by or on behalf of any indemnified party.

(d)Settlement without Consent if Failure to Reimburse. If at any time an indemnified party shall have requested an indemnifying party to reimburse the indemnified party for fees and expenses of counsel, such indemnifying party agrees that it shall be liable for any settlement of the nature contemplated by Section 6(a)(ii) effected without its written consent if (i) such settlement is entered into more than 45 days after receipt by such indemnifying party of the aforesaid request, (ii) such indemnifying party shall have received notice of the terms of such settlement at least 30 days prior to such settlement being entered into, and (iii) such indemnifying party shall not have reimbursed such indemnified party in accordance with such request prior to the date of such settlement.

SECTION 7. Contribution.

(a)If the indemnification provided for in Section 6 hereof is for any reason unavailable to or insufficient to hold harmless an indemnified party in respect of any losses, liabilities, claims, damages or expenses referred to therein; then each indemnifying party shall contribute to the aggregate amount of such losses, liabilities, claims, damages and expenses incurred by such indemnified party, as incurred, (i) in such proportion as is appropriate to reflect the relative benefits received by the Company on the one hand and the Underwriters on the other hand from the offering of the Securities pursuant to this Agreement, or (ii) if the allocation provided by clause (i) is not permitted by applicable law, in such proportion as is appropriate to reflect not only the relative benefits referred to in clause (i) above but also the relative fault of the Company on the one hand and of the Underwriters on the other hand in connection with the statements or omissions, which resulted in such losses, liabilities, claims, damages or expenses, as well as any other relevant equitable considerations.

(b)The relative benefits received by the Company on the one hand and the Underwriters on the other hand in connection with the offering of the Securities pursuant to this Agreement shall be deemed to be in the same respective proportions as the total net proceeds from the offering of the Securities pursuant to this Agreement (before deducting expenses) received by the Company and the total underwriting discount received by the Underwriters, in each case as set forth on the cover of the Prospectus, bear to the aggregate initial public offering price of the Securities as set forth on such cover.

(c)The relative fault of the Company on the one hand and the Underwriters on the other hand shall be determined by reference to, among other things, whether any such untrue or alleged untrue statement of a material fact or omission or alleged omission to state a material fact relates to

26

information supplied by the Company or by the Underwriters and the parties’ relative intent, knowledge, access to information and opportunity to correct or prevent such statement or omission.

(d)The Company and the Underwriters agree that it would not be just and equitable if contribution pursuant to this Section 7 were determined by pro rata allocation (even if the Underwriters were treated as one entity for such purpose) or by any other method of allocation which does not take account of the equitable considerations referred to above in this Section 7. The aggregate amount of losses, liabilities, claims, damages and expenses incurred by an indemnified party and referred to above in this Section 7 shall be deemed to include any legal or other expenses reasonably incurred by such indemnified party in investigating, preparing or defending against any litigation, or any investigation or proceeding by any governmental agency or body, commenced or threatened, or any claim whatsoever based upon any such untrue or alleged untrue statement or omission or alleged omission.

(e)Notwithstanding the provisions of this Section 7, no Underwriter shall be required to contribute any amount in excess of the amount by which the total price at which the Securities underwritten by it and distributed to the public were offered to the public exceeds the amount of any damages which such Underwriter has otherwise been required to pay by reason of any such untrue or alleged untrue statement or omission or alleged omission.

(f)No person guilty of fraudulent misrepresentation (within the meaning of Section 11(f) of the 1933 Act) shall be entitled to contribution from any person who was not guilty of such fraudulent misrepresentation.

(g)For purposes of this Section 7, each person, if any, who controls an Underwriter within the meaning of Section 15 of the 1933 Act or Section 20 of the 1934 Act shall have the same rights to contribution as such Underwriter, and each director of the Company, each officer of the Company who signed the Registration Statement, and each person, if any, who controls the Company within the meaning of Section 15 of the 1933 Act or Section 20 of the 1934 Act shall have the same rights to contribution as the Company. The Underwriters’ respective obligations to contribute pursuant to this Section 7 are several in proportion to the principal amount of Securities set forth opposite their respective names in Schedule A hereto and not joint.

SECTION 8. Representations, Warranties and Agreements to Survive Delivery. All representations, warranties and agreements contained in this Agreement or in certificates of officers of the Company or any of its subsidiaries submitted pursuant hereto, shall remain operative and in full force and effect, regardless of any investigation made by or on behalf of any Underwriter or controlling person, or by or on behalf of the Company, and shall survive delivery of and payment for the Securities to the Underwriters.

SECTION 9. Termination of Agreement.

(a)Termination; General. The Representatives may terminate this Agreement, by notice to the Company, at any time at or prior to the Closing Time (i) if there has been, since the time of execution of this Agreement or since the respective dates as of which information is given in the General Disclosure Package, any material adverse change in the condition, financial or otherwise, in

27

the earnings or business affairs of the Company and its subsidiaries considered as one enterprise, whether or not arising in the ordinary course of business, or any developments involving a prospective material adverse change of the Company and its subsidiaries considered as one enterprise, whether or not arising in the ordinary course of business, (ii) if there has occurred after the date hereof and prior to the Closing Time any material adverse change in the financial markets in the United States or the international financial markets, any outbreak of hostilities or escalation thereof or other calamity or crisis or any change or development involving a prospective change in national or international political, financial or economic conditions, in each case the effect of which is such as to make it, in the reasonable judgment of the Representatives, impracticable to market the Securities or to enforce contracts for the sale of the Securities, (iii) if trading in any securities of the Company has been suspended or materially limited by the Commission or the Nasdaq Stock Market LLC, or if trading generally on the NYSE American, the New York Stock Exchange or the Nasdaq Global Market has been suspended or materially limited, or minimum or maximum prices for trading have been fixed, or maximum ranges for prices have been required, by any of said exchanges or by such system or by order of the Commission, the Financial Industry Regulatory Authority or any other governmental authority, (iv) if a banking moratorium has been declared by either federal or New York authorities, or (v) if a material disruption has occurred in securities settlement or clearance services in the United States.

(b)Liabilities. If this Agreement is terminated pursuant to this Section 9, such termination shall be without liability of any party to any other party except as provided in Section 4 hereof, and provided, further, that Section 1, Section 6, Section 7, Section 8, and Section 15 hereof shall survive such termination and remain in full force and effect.

SECTION 10. Default by One or More of the Underwriters. If one or more of the Underwriters shall fail at the Closing Time to purchase the Securities which it or they are obligated to purchase under this Agreement (the “Defaulted Securities”), the Representatives shall have the right, within 24 hours thereafter, to make arrangements for one or more of the non-defaulting Underwriters, or any other underwriters, to purchase all, but not less than all, of the Defaulted Securities in such amounts as may be agreed upon and upon the terms herein set forth; if, however, the Representatives shall not have completed such arrangements within such 24‑hour period, then:

(a)if the aggregate principal amount of Defaulted Securities does not exceed 10% of the aggregate principal amount of Securities to be purchased on such date, each of the non-defaulting Underwriters shall be obligated, severally and not jointly, to purchase the full amount thereof in the proportions that their respective underwriting obligations hereunder bear to the underwriting obligations of all non-defaulting Underwriters, or

(b)if the aggregate principal amount of Defaulted Securities exceeds 10% of the aggregate principal amount of Securities to be purchased on such date, this Agreement shall terminate without liability on the part of any non-defaulting Underwriter.

No action taken pursuant to this Section 10 shall relieve any defaulting Underwriter from liability in respect of its default.

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In the event of any such default which does not result in a termination of this Agreement, either the Representatives or the Company shall have the right to postpone the Closing Time for a period not exceeding seven days in order to effect any required changes in the Registration Statement or Prospectus or in any other documents or arrangements. As used herein, the term “Underwriter” includes any person substituted for an Underwriter under this Section 10.

SECTION 11. Certain Agreements of the Underwriters. Each Underwriter hereby represents and agrees that:

(a)it has not used, authorized the use of, referred to or participated in the planning for use of, and will not use, authorize the use of, refer to or participate in the planning for use of, any “free writing prospectus”, as defined in Rule 405 of the 1933 Act Regulations (which term includes use of any written information furnished to the Commission by the Company and not incorporated by reference into the Registration Statement and any press release issued by the Company) other than (i) a free writing prospectus that contains no “issuer information” (as defined in Rule 433(h)(2) of the 1933 Act Regulations) that was not included (including through incorporation by reference) in any preliminary prospectus or a previously filed Issuer Free Writing Prospectus, (ii) any Issuer Free Writing Prospectus listed on Schedule B or prepared pursuant to Section 3(o) hereof (including any electronic road show), (iii) any free writing prospectus prepared by such underwriter and approved by the Company in advance in writing, or (iv) any free writing prospectus prepared by or on behalf of such underwriter that would not be required to be filed with the Commission;

(b)it has not and will not, without the prior written consent of the Company, use any free writing prospectus that contains the final terms of the Securities, unless such terms have previously been included in a free writing prospectus filed with the Commission; provided that the Underwriters may use a term sheet substantially in the form of Schedule C hereto without the consent of the Company; provided, further, that any Underwriter using such term sheet shall notify the Company, and provide a copy of such term sheet to the Company, prior to, or substantially concurrently with, the first use of such term sheet and, provided, further, that nothing in this Section 11 shall prevent the Underwriters from transmitting or otherwise making use of one or more customary “Bloomberg Screens” to offer the Securities or convey final pricing terms thereof that contain only information contained in the term sheet attached as Schedule C hereto;

(c)(i) it has only communicated or caused to be communicated and will only communicate or cause to be communicated an invitation or inducement to engage in investment activity (within the meaning of Section 21 of the U.K. Financial Services and Markets Act of 2000 (the “FSMA”)) received by it in connection with the issue or sale of the Securities in circumstances in which Section 21(1) of the FSMA does not apply to the Company; and (ii) it has complied with and will comply with all applicable provisions of the FSMA with respect to anything done by it in relation to the Securities in, from or otherwise involving the United Kingdom; and

(d)solely in connection with the offering of the Securities, it has not made and will not make an offer of, or otherwise made or will make available, the Securities to any retail investor in the European Economic Area. For the purposes of this provision, “a retail investor” means a person who is one (or more) of: (i) a retail client as defined in point (11) of Article 4(1) of Directive 2014/65/EU (as amended, “MiFID II”); (ii) a customer within the meaning of Directive 2002/92/

29

EC, as amended, where that customer would not qualify as a professional client as defined in point (10) of Article 4(1) of MiFID II; or (iii) not a qualified investor as defined in Directive 2003/71/EC.

SECTION 12. Notices. (a) All notices and other communications hereunder shall be in writing and shall be deemed to have been duly given if mailed, hand delivered, couriered, facsimiled or transmitted by any standard form of telecommunication and confirmed to the parties hereto as follows:

(i)    If to the Representatives:

BofA Securities, Inc.

114 West 47th Street

NY8-114-07-01

New York, New York 10036

Attention: High Grade Transaction Management/Legal

Facsimile: (212) 901-7881

MUFG Securities Americas Inc.

1221 Avenue of the Americas, 6th Floor

New York, New York 10020

Attention: Capital Markets Group

Facsimile: (646) 434-3455

Barclays Capital Inc.

745 Seventh Avenue

New York, New York 10019

Attention: Syndicate Registration

Facsimile: (646) 834-8133

Goldman Sachs & Co. LLC

200 West Street

New York, New York 10282

Attention: Registration Department

Email: registration-syndops@ny.email.gs.com

and

J.P. Morgan Securities LLC

383 Madison Ave

New York, NY, 10179

Attention: Investment Grade Syndicate Desk

Facsimile: (212) 834-6081

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with a copy to:

Gibson, Dunn & Crutcher LLP

200 Park Avenue

New York, NY 10166

Facsimile: 212-351-5237

Attention: Andrew L. Fabens

(ii)    If to the Company:

Alliant Energy Corporation

4902 N. Biltmore Lane

Madison, Wisconsin 53718

Facsimile: (608) 458-0132

Attention: Treasurer

with a copy to:

Perkins Coie LLP 1301 Second Avenue Suite 4200

Seattle, WA 98101

Facsimile: (206) 359-9000

Attention: Allison Handy

(b) Any party hereto may change the address or facsimile number for receipt of communications by giving written notice to the other parties hereto.

SECTION 13. Parties. This Agreement shall inure to the benefit of and be binding upon each of the Underwriters and the Company and their respective successors. Nothing expressed or mentioned in this Agreement is intended or shall be construed to give any person, firm or corporation, other than the Underwriters and the Company and their respective successors and the controlling persons and officers and directors referred to in Section 6 and Section 7 hereof and their heirs and legal representatives, any legal or equitable right, remedy or claim under or in respect of this Agreement or any provision herein contained. This Agreement and all conditions and provisions hereof are intended to be for the sole and exclusive benefit of the Underwriters and the Company and their respective successors, and said controlling persons and officers and directors and their heirs and legal representatives, and for the benefit of no other person, firm or corporation. No purchaser of Securities from any Underwriter shall be deemed to be a successor by reason merely of such purchase.

SECTION 14. No Fiduciary Duty. The Company hereby acknowledges that the Underwriters will be acting pursuant to a contractual relationship on an arm’s length basis and in no event do the parties intend that the Underwriters act or be responsible as a fiduciary to the Company, its management, stockholders, creditors or any other person. The Company and the Underwriters each hereby expressly disclaim any fiduciary relationship and agree they are each responsible for making their own independent judgments with respect to any transactions entered into between them.

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SECTION 15. GOVERNING LAW AND TIME. THIS AGREEMENT AND ALL DISPUTES, CONTROVERSIES OR CLAIMS ARISING OUT OF OR RELATING TO THIS AGREEMENT OR A BREACH HEREOF SHALL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK. EXCEPT AS OTHERWISE SET FORTH HEREIN, SPECIFIED TIMES OF DAY REFER TO NEW YORK CITY TIME.

SECTION 16. Patriot Act. In accordance with the requirements of the USA Patriot Act (Title III of Pub. L. 107-56 (signed into law October 26, 2001)), the Underwriters are required to obtain, verify and record information that identifies their clients, which may include the name and address of their clients, as well as other information that will allow the Underwriters to properly identify their clients.

SECTION 17. Recognition of the U.S. Special Resolution Regimes.

(a)In the event that any Underwriter that is a Covered Entity (as defined below) becomes subject to a proceeding under a U.S. Special Resolution Regime (as defined below), the transfer from such Underwriter of this Agreement, and any interest and obligation in or under this Agreement, will be effective to the same extent as the transfer would be effective under the U.S. Special Resolution Regime if this Agreement, and any such interest and obligation, were governed by the laws of the United States or a state of the United States.

(b)In the event that any Underwriter that is a Covered Entity or a BHC Act Affiliate (as defined below) of such Underwriter becomes subject to a proceeding under a U.S. Special Resolution Regime, Default Rights (as defined below) under this Agreement that may be exercised against such Underwriter are permitted to be exercised to no greater extent than such Default Rights could be exercised under the U.S. Special Resolution Regime if this Agreement were governed by the laws of the United States or a state of the United States.

For purposes of this Section 17:

“BHC Act Affiliate” has the meaning assigned to the term “affiliate” in, and shall be interpreted in accordance with, 12 U.S.C. § 1841(k).

“Covered Entity” means any of the following:

i.a “covered entity” as that term is defined in, and interpreted in accordance with, 12 C.F.R. § 252.82(b);

ii.a “covered bank” as that term is defined in, and interpreted in accordance with, 12 C.F.R. § 47.3(b); or

iii.a “covered FSI” as that term is defined in, and interpreted in accordance with, 12 C.F.R. § 382.2(b).

“Default Right” has the meaning assigned to that term in, and shall be interpreted in accordance with, 12 C.F.R. §§ 252.81, 47.2 or 382.1, as applicable.

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“U.S. Special Resolution Regime” means each of (i) the Federal Deposit Insurance Act and the regulations promulgated thereunder, and (ii) Title II of the Dodd-Frank Wall Street Reform and Consumer Protection Act and the regulations promulgated thereunder.

SECTION 18. Effect of Headings. The Article and Section headings herein and the Table of Contents are for convenience only and shall not affect the construction hereof.

SECTION 19. Counterparts. This Agreement may be executed in any number of counterparts, each of which shall be deemed to be an original, but all such counterparts shall together constitute one and the same Agreement. Counterparts may be delivered via facsimile, electronic mail (including any electronic signature covered by the U.S. federal ESIGN Act of 2000, Uniform Electronic Transactions Act, the Electronic Signatures and Records Act or other applicable law, e.g., www.docusign.com) or other transmission method and any counterpart so delivered shall be deemed to have been duly and validly delivered and be valid and effective for all purposes.

[Signature pages follow]

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If the foregoing is in accordance with your understanding, please sign and return to us counterparts hereof, and upon the acceptance hereof by you, on behalf of the Underwriters, this letter and such acceptance hereof shall constitute a binding agreement between the Underwriters and the Company.

Very truly yours,
Alliant Energy Corporation
By:	/s/ Benjamin Bilitz
	Name: Benjamin Bilitz
	Title:   Treasurer

[Signature Page to Underwriting Agreement]

CONFIRMED AND ACCEPTED, as of the date first above written:
BofA Securities, Inc.
By:	/s/ Rob Colucci
	Name: Rob Colucci
	Title:   Managing Director
MUFG Securities Americas Inc.
By:	/s/ Maheen Baig
	Name: Maheen Baig
	Title:   Managing Director
Barclays Capital Inc.
By:	/s/ John Lembeck
	Name: John Lembeck
	Title:   Managing Director
Goldman Sachs & Co. LLC
By:	/s/ Kevin Dirkse
	Name: Kevin Dirkse
	Title:   Managing Director
J.P. Morgan Securities LLC
By:	/s/ Robert Bottamedi
	Name: Robert Bottamedi
	Title:   Executive Director

For themselves and as Representatives of the other Underwriters named in Schedule A hereto.

[Signature Page to Underwriting Agreement]

SCHEDULE A

LIST OF UNDERWRITERS’ PURCHASE AMOUNTS

Name of Underwriter	Principal amount of Securities to be purchased
BofA Securities, Inc.	$145,000,000
MUFG Securities Americas Inc.	$145,000,000
Barclays Capital Inc.	$120,834,000
Goldman Sachs & Co. LLC	$120,833,000
J.P. Morgan Securities LLC	$120,833,000
Mizuho Securities USA LLC	$36,250,000
Wells Fargo Securities, LLC	$36,250,000
Total	$725,000,000

Schedule A-1

SCHEDULE B

ISSUER FREE WRITING PROSPECTUSES

Final Term Sheet, dated September 23, 2025.

Schedule B-1

SCHEDULE C

Issuer Free Writing Prospectus

Filed Pursuant to Rule 433

Registration Statement No. 333-276062

ALLIANT ENERGY CORPORATION

Final Term Sheet

September 23, 2025

5.750% Fixed-to-Fixed Reset Rate Junior Subordinated Notes due 2056

This issuer free writing prospectus relates only to the securities described below and should be read together with Alliant Energy Corporation’s preliminary prospectus supplement dated September 23, 2025 (the “Preliminary Prospectus Supplement”), the accompanying prospectus dated September 22, 2025 and the documents incorporated and deemed to be incorporated by reference therein.

Issuer:	Alliant Energy Corporation (the “Company”)
Aggregate Principal Amount Offered:	$725,000,000
Anticipated Ratings*:	Baa3 / BBB- (Moody’s / S&P)
Trade Date:	September 23, 2025
Settlement Date:	September 26, 2025 (T+3)
Maturity:	April 1, 2056
Interest Payment Dates:	April 1 and October 1
Record Dates for Interest Payment:	March 15 or September 15
First Interest Payment Date:	April 1, 2026
Security Type:	5.750% Fixed-to-Fixed Reset Rate Junior Subordinated Notes due 2056 (the “notes”)

Schedule C-1

Interest Rate:	The notes will bear interest (i) from and including September 26, 2025 (which is the expected original issuance date) to, but excluding, April 1, 2031 (the “First Reset Date”) at the rate of 5.750% per annum and (ii) from and including the First Reset Date, during each Reset Period (as defined in the Preliminary Prospectus Supplement), at a rate per annum equal to the Five-year U.S. Treasury Rate (as defined in the Preliminary Prospectus Supplement) as of the most recent Reset Interest Determination Date (as defined in the Preliminary Prospectus Supplement) plus a spread of 2.077%, to be reset on each Reset Date (as defined below); provided, that the interest rate during any Reset Period will not reset below 5.750% per annum (which equals the initial interest rate on the notes). For more information regarding the interest rate for the notes, see “Description of the Notes— Interest Rate and Maturity” in the Preliminary Prospectus Supplement.
Reset Date:	First Reset Date and April 1 of every fifth year after 2031.
Option to Defer Interest Payments:	So long as no event of default with respect to the notes has occurred and is continuing, the Company may, at its option, defer payment of all or part of the current and accrued interest otherwise due on the notes, on one or more occasions, for one or more Optional Deferral Periods (as defined in the Preliminary Prospectus Supplement) of up to 20 consecutive Interest Payment Periods (as defined in the Preliminary Prospectus Supplement). A deferral of interest payments may not end on a date other than the day immediately preceding an interest payment date and may not extend beyond the maturity date of the notes, and the Company may not begin a new Optional Deferral Period and may not pay current interest on the notes until it has paid all accrued interest on the notes from the previous Optional Deferral Period. For more information concerning the Company’s option to defer interest payments, see “Description of the Notes--Option to Defer Interest Payments” in the Preliminary Prospectus Supplement.

Schedule C-2

Optional Redemption Provisions:	The Company may redeem some or all of the notes, at its option, in whole or in part, (i) on any day in the period commencing on the date falling 90 days prior to the First Reset Date and ending on and including the First Reset Date and (ii) after the First Reset Date, on any interest payment date, at a redemption price in cash equal to 100% of the principal amount of the notes being redeemed, plus, subject to the terms described in the first paragraph under “Description of the Notes— Redemption Procedures; Cancellation of Redemption” in the Preliminary Prospectus Supplement, accrued and unpaid interest on the notes to be redeemed to, but excluding, the redemption date. The Company may at its option redeem the notes, in whole but not in part, at any time following the occurrence and during the continuance of a Tax Event (as defined in the Preliminary Prospectus Supplement) at a redemption price in cash equal to 100% of the principal amount of the notes, plus, subject to the terms described in the first paragraph under “Description of the Notes—Redemption Procedures; Cancellation of Redemption” in the Preliminary Prospectus Supplement, accrued and unpaid interest on the notes to, but excluding, the redemption date. The Company may at its option redeem the notes, in whole but not in part, at any time following the occurrence and during the continuance of a Rating Agency Event (as defined in the Preliminary Prospectus Supplement) at a redemption price in cash equal to 102% of the principal amount of the notes, plus, subject to the terms described in the first paragraph under “Description of the Notes— Redemption Procedures; Cancellation of Redemption” in the Preliminary Prospectus Supplement, accrued and unpaid interest on the notes to, but excluding, the redemption date. For additional information and the definitions of the terms Tax Event and Rating Agency Event, see “Description of the Notes—Redemption” in the Preliminary Prospectus Supplement.
Price to Public:	100.000% of the principal amount, plus accrued interest, if any.
Proceeds to the Company Before Expenses:	99.000% of the principal amount
CUSIP:	018802 AF5

Schedule C-3

ISIN:	US018802AF54
Joint Book-Running Managers:	BofA Securities, Inc. MUFG Securities Americas Inc. Barclays Capital Inc. Goldman Sachs & Co. LLC J.P. Morgan Securities LLC Mizuho Securities USA LLC Wells Fargo Securities, LLC

* A securities rating is not a recommendation to buy, sell or hold securities and may be subject to revision or withdrawal at any time.

It is expected that delivery of the notes will be made against payment therefor on or about September 26, 2025, which will be the third business day following the date of pricing of the notes. Under Rule 15c6-1 of the Securities Exchange Act of 1934, trades in the secondary market generally are required to settle in one business day, unless the parties to any such trade expressly agree otherwise. Accordingly, by virtue of the fact that the notes initially will settle in T+3, purchasers who wish to trade the notes on any date prior to the business day before delivery should specify an extended settlement cycle at the time they enter into any such trade to prevent failed settlement and should consult their own advisors.

The issuer has filed a registration statement (including a prospectus) with the Securities and Exchange Commission (the “SEC”) for the offering to which this communication relates. Before you invest, you should read the prospectus in that registration statement and other documents that the issuer has filed with the SEC for more complete information about the issuer and this offering. You may get these documents for free by visiting EDGAR on the SEC website at www.sec.gov. Alternatively, you may request a copy of these documents by calling BofA Securities, Inc. toll free at 1-800-294-1322, MUFG Securities Americas Inc. toll free at 1-877-649-6848, Barclays Capital Inc. toll free at (888) 603-5847, Goldman Sachs & Co. LLC toll-free at 1-866-471-2526 and J.P. Morgan Securities LLC collect at 1-212-834-4533.

Any legends, disclaimers or other notices that may appear below are not applicable to this communication and should be disregarded. Such legends, disclaimers or other notices have been automatically generated as a result of this communication having been sent via Bloomberg or another system.

Schedule C-4

SCHEDULE D

UNDERWRITER INFORMATION

1.The statements set forth in the second paragraph under the heading “Commissions and Discounts” in the section titled “Underwriting” in the Prospectus and in any preliminary prospectus.

2.The statements set forth in the first and second paragraphs under the heading “Price Stabilization and Short Position” in the section titled “Underwriting” in the Prospectus and in any preliminary prospectus.

Schedule D-1